Glacial Period on the present fauna of N. America. 181 



venture to add that before beginning this enquiry I had no idea 

 what the result of my tabulation would prove. 



In the following discussion of the question, I shall limit 

 myself to the use of insects, and indeed of a single order of 

 insects, as subjects for illustration ; not only because some 

 limitation must be made in this place with so large a subject 

 before us, but also, and principally, because insects may rightly 

 be regarded as better tests than any other group of animals or 

 than any group of plants, in nice questions of distribution either 

 in space or time. This is not generally acknowledged, but a 

 single pertinent illustration will suffice. 



It is well known that as we pass upward in the Tertiary 

 period there is a growing resemblance of the animals and 

 plants of its different subdivisions to those living at the 

 present time ; a resemblance both in general and in particular, 

 an increasing percentage of forms regarded as identical or 

 nearly identical with existing types being found as one passes 

 from the Eocene to the present time. Furthermore the plants 

 and (leaving the mammals out of account) the known ani- 

 mals of the Quaternary are, with extremely rare exceptions, 

 identified altogether with those now living. Nearly all the 

 mammals are extinct. Now, although the main broad features 

 of insect life appear to have been much the same in the early 

 Tertiary as now, not only has not a single Tertiary insect been 

 shown to be living at the present day, whether in Europe or 

 America, but a considerable proportion of Quaternary insects 

 have also been described as extinct. It is true that a few, a 

 dozen or two, Tertiary insects have been listed as belonging to 

 existing forms, but in each such case the determination has 

 been made by one not conversant with insects, or else with no 

 statement of the basis or terms of comparison. 



As to the Quaternary insects, I find in Europe 80 Coleoptera 

 which have been studied with more or less care ; of these 13 

 are treated as extinct and 67 identified more or less confidently 

 with existing European forms. This number however, it 

 should be insisted upon, is made up very largely of remains 

 from peat bogs, which are relatively very recent. In our own 

 country, 48 species of pleistocene Coleoptera have been 

 described,* of which only a single one is regarded as probably 

 identical with an existing form, three are specifically inde- 

 terminate and 44 are extinct, though in some cases intimateiy 

 allied to forms now living. I add a list of these. 



* Including five species from Hadley, Mass., described in an uDpublisied 

 memoir. 



